1. Field of the Invention
The present invention relates to a polishing pad and a method for making the same, and in particular, to a polishing pad having a fiber substrate and a method for making the same.
2. Description of the Related Art
The conventional polishing pad substantially can be divided into two types: a non-woven polishing pad and a separate foam polishing pad. The conventional non-woven polishing pad includes a plurality of fibers and a resin, and the polishing pad is manufactured by using a composite material of the fibers (such as velvet or suede) and the resin, or impregnating a non-woven fabric formed by the fibers in a thermoplastic polyurethane resin for wet coagulation to form a flexible sheet having high deformability formed. A disadvantage of the polishing pad is that the flexibility thereof may easily lead to poor planarization performance of its grinding surface, and the resin cannot uniformly enclose the fibers, that is, a portion of the fibers are not enclosed by the resin, resulting in that the overall strength is insufficient and the service life is shorter.
The conventional separate foam polishing pad includes a plurality of pores and a resin, and the polishing pad is manufactured by pouring the resin (generally a polymer foam of thermoplastic polyurethane) into a cylindrical mold, cooling the resin for coagulation, and then slicing the resin. The polishing pad has higher rigidity than the first conventional non-woven polishing pad, has separate pore structures, and is usually used for high planarization polishing. However, the major problem of the polishing pad is that since it is difficult to achieve uniform distribution of the concentration of the resin in the cylindrical mold, non-uniform temperature distribution at positions in the cylindrical mold during the molding process may lead to different sizes and non-uniform distribution of the pores, which are not easy to be controlled, and as a result, after the slicing process, the difference between the sizes of the pores on the sliced surface of the polishing pad becomes more significant. Moreover, the pores are not in communication with each other, and polishing slurry may not easily flow therebetween in use, and is apt to scratch a workpiece.
Therefore, it is necessary to provide an innovative and progressive polishing pad and a method for making the same, so as to solve the above problems.